Disclosed is a method for increasing production efficiency of mold lines where molten metal or other material requiring a cooling period is poured sequentially into moving molds. The invention particularly comprehends the tracking of individual molds and the individualized control of the cooling time of the molds from beginning to end of the line in the presence of random line stoppages and variant mold size.
Automatically controlled pouring lines for molten metal in foundries re discussed in patents and applications by the inventors such as U.S. Pat. No. 4,724,894 aid WO 97/20651, of which this application is a continuation in part.
To get proper quality of castings made in a typical xe2x80x9cDISAMATICxe2x80x9d or other vertical parted molding line, it""s essential that the cast iron parts remain in their sand mold for a certain time period based on the cross section of parts plus the iron/sand ratio. This cooling time is typically 30-50 minutes.
However, many foundries operating high production molding lines of this type, can""t utilize the potential line speed made possible by the ability of the mole making machine to create the molds, because of inadequate cooling time provided by the short lengths of cooling sections caused by plant size constraints and other factors. They must slow down the production speed (MPH, or molds per hour) in order to get sufficient cooling time.
For example, let us take the case of a vertical ported molding line containing a molding machine, (for example by Disamatic) whose potential speed is 400 molds per hour. (see also referenced co-pending application WO 97120651 of the inventors incorporated herein by reference) Assuming, as is often the case, a length of cooling section in the line of 40 m, and that each mold size is 250 mm. in the direction of line flow (noting that mold size varies, and is measured either by the mold making machine, or automated pouring machine, if present). Required cooling time for this particular model is assumed to be 36 minutes. This then gives a resultant average rate mold speed of 240 parts per hour, so limited in order to not let any mold get out of the cooling sections until the required time have expired.
The mold making machine cycle time has thus been slowed from a potential of 400 to 240 which only is 60 percent utilization of the machine. The solution of this problem is to extend the cooling section but this is often impossible or impractical due to economic issues or physical limits.
In addition, the above example is calculated assuming the production line has no stoppages or waiting situations during production. Typically however, a foundry has waiting times of around 6-10 minutes per hour caused by pattern changes (used to create the molds), waiting for iron and sand, equipment failure or whatever the reason might be. So instead of making 240 good molds and parts therefore, they only sake 200 due to a down time of 10 minutes.
There is no prior art known to the inventors addressed to solving this additional problem of lost production due to stoppages or other waiting time delays in such lines. Nor is there any present method to account individually for variation in mold size in so far as cooling time is concerned.
An automated pouring system, such as the xe2x80x9cLaserPourxe2x80x9d system which has evolved from that described in the referenced patents above and often used today to control pouring of metal, is designed to determine information on each mold produced in the molding machine to manage the positioning feature of the pouring vessel so as to fill the pouring cup properly with the molten metal stream. One piece of information obtained is mold size (although in certain modern molding lines, this information is also available from the mold making machine). Mold size can vary, particularly in the line direction (length direction), due to a variety of factors, including compressibility variation in the sand making up a mold, as is often used in iron foundries. By storing data such as mold size and pour height (if different) on all molds in a buffer, the entire mold stack (i.e., group of sequentially poured molds) can be monitored from the time it was poured until it reaches the end of cooling section. The LaserPour system, for example, by utilizing the invention herein, can control the cycle time of the molding machine preceding the pouring station by delaying the release signal for next index.
To produce 240 molds per hour the pouring machine cycle time should average 15 seconds. As noted above, a stop of the production of even 5 minutes results in a loss of 20 molds. When the production starts again the Cooling Time Control function of the invention will increase the line speed to the maximum until the 5 Minutes stopping time (during which cooling was however occurring) has been recovered, then it will go back to nominal 240 MPH again, providing that a second stop occurs within the stipulated cooling time of the mold. This is done with full control so no mold will leave the cooling section prior to the required cooling timexe2x80x94an added quality assurance as well. If however a mold is to be pushed out without having accumulated the stipulated cooling time, the system will hold the mold line.
Over all, we have found the productivity increase on the line is generally few percent depending on the mix of parts produced with various required cooling times. This is very important, as every percent increase in production of such lines typically represents $225,000 in increased revenue with an added profit of more than $100,000 per year.
It is a goal of the invention to increase productivity of typical mold lines in the foundry businessxe2x80x94resulting in very large dollar savings even for a few percept added production.
It is a further goal of the invention to insure that quality of the castings produced can be kept within specification by individual consideration of mold cooling time.
It is a still further goal of the invention to achieve the above at economical initial and operating cost.